Drawer type high-speed interlens shutter



Oct. 12, I954 P, LLCOX 2,691,331

DRAWER TYPE HIGH-SPEED INTERLENS SHUTTER Filed Nov. 4, 1949 4 Sheets-Sheet l [Feds/Lek P M06076 BY W M %T $\IEY INVENTOR.

1954 F. P. WILLCOX 31 DRAWER TYPE HIGH-SPEED INTERLENS SHUTTER Filed NOV. 4, 19 49 4 Sheets-Sheet 2 4 Meclenick I. WZJJcox,

BY k

ATTORNEY 'INVENTOR Oct. 12, 1954 F. P. w|| cox 2,691,331

' DRAWER TYPE HIGH-SPEED INTERLENS SHUTTER Filed Nov. 4, 1949 4 Sheets-Sheet 5 INVENTOR:

Mada/ck l? 71 4' c0x ATTORNEY DRAWER TYPE HIGH-SPEED INTERLENS SHUTTER Filed Nov. 4, 1949 4 Sheets-Sheet 4 INVENTOR edcrck fwllcozi BY MW ATTORNEY Patented Oct. 12, 1954 DRAWER TYPE HIGH-SPEED INTERLENS SHUTTER cFrederick P. 'Willcox; Westmoreland Hills, Md., assignor to Fairchild Cameraand Instrument Corporation, a corporation of Delaware Application November 4, 1949, Serial No. 125,453

I 8 Claims. 1

This invention relates to photographyiand' particularly to photographic shutters of. thetype especially adapted for aerial photography.

The special operational requirements of aerial photography have in general'resulted in aerial camera shutter designs which are characterized by heavy and massiveconstructions requiring relatively large amounts of power: for: operation at high shutter-speeds. Since theamountof power which can conveniently be applied to'the driving of shutter components is'limited, such designs have in'general not-:beencapable of'the maximum speeds required for use withmodern films and emulsions. Also, thexnecessityfor sudden stopping of relatively massive-moving parts in these prior shutters has involved considerable shake or jar of the camera itself during exposure which is of course very detrimental to image definition, as well as possibly injurious-to-delicate camera and shutter parts.

Another disadvantage'of many'iormerdesigns of aerial camera shutters is that it has-generally been necessary to removethe-ent-ire shutter and camera lens assembly from the camera when repairs or adjustments have had to be made to the shutten In precision aerial-mapping cameras, this means that the camera must-berecalibrated when the lens andshutter assembly is reassembled to the camera. Suchrecalibration is expensive and time consuming, requires a'higndeg-ree of skill and can only be accomplished'in a very few laboratories. This i objection is rendered -more serious by the factthat the massive construction of the known aerial oamera'shutters, and-theconsequently large forces which-are employed to drive the parts, render the necessity for adjustment and repair of more frequent-occurrence than would-be expected'in' the case of shutters using lighter parts and lowermagnitu-des of'opcrating force.

It is consequently a principal object of the present invention to provide a photographic "shutter for aerial" camera use which will bis-constructed of parts which are in generalmuch lightefthan those heretofore employed, to provide ahigher reliable maximum exposure speed by the use of relatively small operating forces.

Another object of the invention is to provide a camera shutter which will achieve-thevdesired high-speed of exposure without causing-anyperceptible'shake of" the lens components or of the camera itself, thusenabling-the production of images with a high-degree of definition.

still another object of the invention is to "provide an aerial camera shutter which will require only a moderate amount'of driving power considering the high speeds obtained.

' A further object of. the invention is to provide aerialcamera shutters in such form that those parts which must of necessity be located between components 05' the lenssassembly can be slipped laterally in and=out of said lens assembly as a unit, without the -necessitylfor disturbing the lens assembly. This drawer.construction makes it possible to remove the complete shutter for adjustment or repair without involving any of. the precision optical work involved in'the removal or disassemblyof existing types of aerial camera shutters used with precision mapping lenses.

Still another object of the invention is to provide a shutter of theabove type with improved stopping mechanisms 'for the shutter driving members, which will enable theseparts also to be deceleratedinsuch a wayzas to eliminate shock and vibration.

An additional object is-to provide animproved combined brake member and latch, especially for use where the main driving member of the shutter rotates through a complete revolution for each exposure cycle, and rotateszinthe same direction forsuccessive exposure cycles.

In generaL'the. above objects of the invention are best obtained by a shutter design utilizing two'separate sets of bladesyoneset having the function of'uncovering' the optical aperture to initiate an exposure, and the other set having the function of coveringsaid aperture to termihate the exposure, together with a positive and adjustable-mechanism for accomplishing the release of the second set of blades at a predetermined time after the blades of the first set have commenced their shutter-opening -movement. These parts, or at least such of them as required to. be-located betweenthe'optical elements of a lens assembly, are so arranged that the axial thickness of thispart of the shutter mechanism is extremelysmall, so'that theshutter may be slipped sidewise fromits. operative position and removed without disturbing the optical portions of: the lens assembly. At the I same time, novel features of blade-control linkage have'been provided which are applicable to shutters having two sets of blades (as above described) and also to more conventional shutters utilizing a single set of blades.

-.An actual embodiment of a shutter provided with two sets of blades and utilizing these design features has been constructed and tested, andhas given a maximum iexposurespeedof 0.9.1milliseconds total time, that is, the elapsed time from the commencement of the opening of the shutter aperture until its complete closure, and this shutter also has a very high optical efficiency. The effectiveness of the individual blade control mechanism considered alone, is demonstrated by the fact that a drawer type shutter having a single set of blades has given speeds of 1.5 milliseconds total time, which is much faster than any other known shutter utilizing blades which reverse their direction of travel between shutter opening and shutter closing movements. Both of the shutters referred to have clear exposure apertures of 0.800 inch.

I am aware that it has heretofore been proposed to provide a camera shutter utilizing separate blades or sets of blades for the functions of uncovering and covering the exposure aperture, in order to avoid the necessity for reversing the direction of movement of a single blade or blades at some point in their movements. However, so far as I am aware it has not been proposed to utilize this principle in connection with individual blade control to provide high speed and efficiency nor in a shutter whose dimensions would enable it to be installed in the extremely limited space between the optical elements of precision mapping lens assemblies.

The above and other objects and advantages of the invention will best be understood by reference to the accompanying drawings, taken in connection with the appended specification, and illustrating a preferred shutter structure in accordance with the principles of the invention.

In the drawings,

Fig. 1 is a plan view, partly broken away, of a drawer type shutter having two sets of operating blades controlled in accordance with the principles of this disclosure, and showing the shutter in wound condition with one set of blades closed and the other open,

Fig. 2 is a view similar to Fig. 1 but looking at the shutter from the opposite direction and with other parts broken away to illustrate the drive and control linkages, the shutter also being in wound condition ready for exposure,

Fig. 3 is a view looking in the same direction as Fig. 2 but with the mechanism in the rundown condition after the making of an exposure,

Fig. 4 is a side elevation of the same shutter Zhowing the relative thinness of the construc- Fig. 5 is a plan view of a different drawer-type shutter having a single set of blades but utilizing the same blade control features as the previous embodiment,

Fig. 6 is a similar view of the shutter of Fig. 5 but with the parts in partially run-down condiion,

gig. 7 is a side elevation of the shutter of Figs. 5 an 6,

Figs. 8 and 9 are diagrammatic illustrations of of the relationship between cranks and links characteristic of both of the shutters illustrated in the drawings,

Fig. 10 is an elevational view showing the shutter inserted in a typical lens assembly,

Fig. 11 is an enlarged sectional view taken on line H-H of Fig. 2,

Fig. 12 is an enlarged fragmentary view of a portion of Fig. 2, and

Fig. 13 is a sectional view taken on line l3--l3 of Fig. 12.

The preferred form of shutter in which I have embodied my invention is of the type utilizing two separate sets of blades lying closely adjacent sets of pivotally mounted blades.

one another, and so arranged that the exposure is commenced by the opening of one (normally closed) set of these blades, while the exposure is terminated by the closure of the second (normally open) set of blades. The expressions normally open and normally closed are used here and throughout the description in reference to the two sets of blades as they stand when the shutter is in wound condition ready for an exposure. By this means, the time ordinarily required for the reversal of movement of a single set of blades in going from opening to closing phases can be reduced to as small a value as desired. However, certain features of the control mechanism and the transmission of power from the driving member to the shutter blades are equally applicable to a shutter of the type having only one set of blades which are reversed durin their travel, and I have therefore also disclosed herein the application of these features to such a simplified shutter.

Referring now particularly to Figs. 1 to 4 and 11 of the drawings, the shutter illustrated therein is of the type having two complete superposed The individual drive and control mechanisms for these sets are brought out laterally from the area occupied by the blades themselves, so that the thickness of the area which must of necessity lie within the lens assembly is reduced to the minimum. The desirability of this feature of the invention is well shown in Fig. 10 of the drawings, which illustrates in sectional View a portion of a conventional and well known mapping lens assembly designated generally by the reference letter L, two of the optical lens elements themselves being designated by letters E and F. This lens mount is provided with a slot designated S in the drawings into which the shutter blade portion of the shutter must be installed, the same being guided into place by guides integral with or affixed to portions of the lens mounting parts. In a particular lens assembly of this type, the clear space between the cells of lens elements E and F is of the order of 0.10 inch, and in order to permit the slidable insertion and removal of the shutter without disassembly of the lens cells from the mounting, the maximum axial thickness of the part of the shutter passing between the cells is necessarily somewhat smaller than this dimension. It is to be understood, however, that the features of the present shutter which achieve this unusual thinness do not limit the same to a slip-in installation, as the shutter presents numerous other features of construction and operation which are desirable in any high-speed, high efiiciency application.

In the interest of economy of manufacture, the parts pertinent to the two sets of blades, such as the blades themselves, the motion transmitting members and the links, are duplicated for the two sets of blades. For this reason, in reading the accompanying drawings it is very difficult to distinguish between the parts relating to the normally open and the normally closed shutter assemblies on the basis of their appearance. A complete understanding of the construction will be facilitated by bearing in mind that the parts relating to the respective blade assemblies are mounted in the respective spaces between a series of three fiat plates arranged in superposed relation, and provided with the necessary cut-outs or recesses necessary to accommodate the parts with adequate clearances. This construction is best illustrated by the side elevational view of Fig. 4 and the sectional View of Fig. 11, in which numeral l0 designates the main or central support plate, while numerals l2 and I 4 respectively designate the cover plates. The set of blades occupying the space between the main plate l0 and the upper plate 12, and its accompanying parts, will be referred to hereinafter as the normally open set of blades, this normally open set of blades being the set which is normally held open when the shutter is in wound condition; the blades of the other set are normally closed, and during an exposure the blades of this latter set are opened and the b ades of the other set are closed in timed relation to the opening of the normally closed set to produce the complete cycle of operations, after which the shutter is rewound in preparation for a following exposure.

Bearing in mind that Figs. 1 and 2 both show the shutter in wound condition, but looking at the assembly from opposite faces, it will be observed that the winding arms or lugs It and iii are each provided with a power spring designated and 22 respectively, one end of each spring engaging the arm or lug and the other being held by a fixed pin on the main plate I0. These winding lugs are secured to shafts 2| and 23 passing through suitable bosses secured to the plate It, and each carries on the underside of the plate ill a latchable crank member, these being designated 24 and 26. As best shown in Fig. 13, which is a fragmentary sectional view taken through winding lug Hi, the latter may be secured to a squared portion of shaft 2| as by a screw, the shaft passing through boss 2! which is secured to plate 50, and said shaft having fixed on its lower end the latchable crank 24. The details of construction of the other spring and winding lug assembly are similar and will be clearly understood from the showing in Fig. 13 and the above description.

The blades constituting the normally closed set are indicated by numeral 28, while the blades constituting the normally open set are designated 30. Referring particularly to Fig. l, the blades 38 are respectively pivoted on the main plate m as at 32, and each is arranged to be driven about its pivot through the agency of a cranked or bent link 34 having at one end a pin .36 pivotally engaging in a driving hole in the blade, and having its opposite end pivoted as at 38 to a crank fan or motion transmitting member 40. There is one of these fans '50 for each of the blades in each set, and each fan is preferably of approximately triangular shape pivoted adjacent one of its vertices upon the main plate it as at 42. In the present embodiment, each set of shutter blades comprises four blades, and the fans corre sponding to these blades are connected in series by means of links 4% whose apertured ends are pivoted as at Mi adjacent the remaining vertices of the fans. It will be seen that each shutter blade is provided with an additional driving hole Mia located symmetrically with reference to the pivot axis 32 of the blade, this hole being provided to enable a single blade configuration to be used for both the normally open and normally closed set of blades. One fan of each set has an additional aperture 48 at which is pivotally connected the link 50 which transmits the driving power to the entire set (see Fig. 1), and the other fans of each set may likewise have this aperture in the interest of manufacturing duplicate parts; this extra aperture in each of the other fans is merely surplusage insofar as operation of the shutter is concerned.

Each set of blades has its own drive mechanism,

6 and the drive mechanisms are substantially identical except for differences to be noted. Referring again to Fig. 1, the particular fan crank 40 appearing at the lower left portion of the upper cover plate l2 receives pivotally in its aperture 48 a pin secured to one end of a short link 56 pivoted in turn to the bell crank 52 pivoted at 54 (see Fig. 2) on the main plate I6. Referring now to Fig. 3, a bent or cranked connecting link 56 is pivoted to the other end of bell crank 52 and to the latchable crank 26 driven by power spring 22 through shaft 23. Fig. 2 illustrates the parts in latched condition, looking at the underside of Fig. 1 and with lower cover plate I4 broken away. The normally closed set of blades 28 is provided with crank fans, cranks and connecting links which are duplicates of those just described, one of the fans being connected by a short link 50 to a bell crank 52 pivoted at 54' on plate l0 and driven through a cranked connecting link 55 pivoted to the latchable crank 24 driven by power spring 20. Latchable crank 24 is held in its wound position by one end of a manual trip lever 58 pivoted at 60 on the main support plate and normally held in latching position by a suitable spring 62. Crank 24 carries a tripping member 64 (see especially Fig. 12) rotatable about the pivot axis of the crank and arranged to be he d in adjusted position thereon by a screw 65 passing through an arcuate slot 68 and threaded into the body of the crank.

A rounded nose It on tripping member M is arranged so that upon release of crank 24 the nose will ultimately smoothly engage a nose E2 on a secondary release lever 14 pivoted to the main support plate at 76, and whose opposite end is normally held in latching engagement with crank 25 by means of aspring 78. Thus, operation of trip lever 58 releases crank 24 to initiate opening movement of blades 28, and at some later time determined by the adjustment of trip ping member 64, the spring tension, and the olelay introduced by any time control mechanism which may be provided, crank 26 is released to permit closing of the other set of blades 30. Each of the cranks 24 and 26 has a curved concave edge 8%! arranged gradually to engage a slightly resilient nose 82 on a braking lever 84 pivoted on the main support plate, the arm 85 of each such lever being in frictional engagement with one spring arm 83 of a brake plate 99 also secured to the plate it. In order to restore the braking levers 84 to their previous positions when the shutter is rewound, each such lever is provided with an additional arm 92 positioned to be engaged by the back edges 9t of the cranks Fi l and 26 during the rewinding movement. The construction just described produces a smooth, vibrationless stop for the main driving cranks and permits them to be decelerated very rapidly without perceptible shock which might affect the quality of an image produced by the exposure.

It will be observed from the above description that the shutter employs two complete and separate sets of shutter blades, and a separate driving mechanism for each of these sets of blades, the mechanism of one set being tripped in predetermined relation to the operation of the other. That is, there is no transmission of operating power from one driving mechanism to the other, and since the tripping time of the blade set last operated is determined in an unvarying (but adjustable) manner in accordance with the actual position of member M, which position is in turn precisely related to the degree of opening of blades=28,'-a1l possibility -of.-tripping of the:sec.

nd. set of bladesat anximproper :time is .elimi-% nated. This system: of independent application of operating power, undervthecontrolwof mem Links. 44 operate in clearance grooves :desig.-

nated t6 and shown in dotted lines in Fig. 2, and by solid lines in the broken away portion of Fig. 3, these grooves being-machined or otherwise formed in the inner surfaces of-the two cover plates [2 and 14. Theshutter blades themselves are pivotally mounted upon opposite sides of the main or central support'plate Ii], which is itself partly broken away in Fig. 3 to show the relationship of one set of blades to the other as well as to the drive linkages. Each of plates 12 and E4 (the former as shown in Fig. 1) is provided with an arcuate clearance slot 4l see also Fig. 11) to receive the link pivot-pins 4S pertaining to each fan 40, An arcuate clearance slot 49 is also provided in each cover plate to receive the end of each pin 36 connecting a link 34 to its corresponding shutter blade.

No particular timing mechanism for the control of the release-of the second set of blades in timed relation to the first set has been described herein, since suchmechanism may be provided in accordance with any desired range of shutter speeds. Similarly, the mechanism for transmitting power to the winding arms or lugs has not been illustrated, also for the reason that the particular arrangements provided are dictated by the special requirements of each application. It is to be understood that this winding mechanism for-controlling the operation of the winding lugs 16 and [8 may take any form so long as it provides for the closure of the open set of blades prior to the opening of the closed set of blades, in order to cap the shutter and prevent exposure of film during the rewinding operation. That is, at the completion of an exposure, with the parts in their Fig. 3 positions, blades 30 are closed and blades'28 are open. To restore the shutter to its wound condition, as in Fig. 1, without exposure of film, all that is necessary is to wind lug l6 (and shaft 2|) completely, to

close blades 28 prior'to the rewinding of lug l8 and shaft 23 to such a position as would open blades 3% When both power springs 20 and 22 have been fully wound, the shutter is ready for the next exposure.

Referring specifically to Fig. 8, it will be seen that at the start of theopening movement of blade 28, the direction of pull of link 34 is approximately perpendicular to the radius drawn from the center of blade rotation 32 to the link connection 38, so that a given movement of link 34 produces a substantial rotation of blade 28. Also, the direction of movement of link 34 lies at a very substantial angle to the radius from the center of fan rotation 42' to connection point 38,

so that a given movement of fan 40 produces a relatively large movement of link 34. Again, the direction of movement of link 44 (which is the direction of its length) makes a substantial angle with a radius from the center of fan rotation 42 to connection point 46. In other words, all of these parts are arranged so that a given movement of link 44 at the starting phase of the blade movement will result in the maximum angular rotation of said blade 28'.

Referring now to Fig.- which also' shows the blades '28 insthe positions they occupy at the,-

start'of the opening; movement, it will be noted that the point of connection of crank 52! with link is slightly toone side ofa line connect-' ing point and point 54' or slightly. off dead center; this arrangement has been found to produce a higher acceleration of the blades 28 r at the beginning of their opening movement thanif these points were in alignment. Also, still referring to Fig.- 2, the point of connection between bent lever 5B.and crank 24 Bin align I overall result of these arrangements is to pro-' duce a very rapid opening movement of blades 28;.

Fig. 9 illustrates diagrammatically the shutter and link relationship nearthe completely opened position of blades 28. Point 38 has moved into its dead centerposition in alignment with points 42 and 36-. Therefore, small movements of'link 44 and fan will contribute practically no mo-- tion to blade 28, and. this complete reversalof transmission ratio not only1'provides a smooth stopping of the blade without any danger. of damaging the parts, but it also insures against rebound of theiblade even if :link 44 should suffer slight rebound movement. Another way of look ing at Fig. 9 is to consider that at the termination of the opening movement'of blade 28, pivot point 38 lies practically at the point of common tangency ofcircles a and b,'so that motion of point 38 about point 36. contributes practically no movementto the blade.. Also, by referring to dash line circleb in Fig. 8, which represents the path of pivotal movement of connection 38 about its center of rotation:.36 -(which also rotates in the. same direction as indicated by dash line circle 0), it is apparent that pivot 36 is brought as close to pivot: 42' as possible to bring circle b into common tangency with circle a which is the condition shown in Fig. 9.0 The significance of this last fact is that as the parts approach their. stopped position, link 34 contributes very little movement to blade 28,-and the combination of all these relationships produces the super-control of the shutter'lades during stopping that is responsible for the absence of destructive forces and of shake and vibration which would otherwise resultif attempt were madeto accelerate and decelerate known blade linkages to produce the speeds obtained with the present shutter.

Referring again to Fig. 3,'it will also be noticed that atthe completion of the opening movement of blades-28, the crank 24 has moved substantially from its Fig.2 position, and the points of connection of bent arm 56 with crank 24 and crank 52 are again practically in alignment with the center of rotation of crank 24 and on dead center. Thus, slight movements of crank 24 will produce very little movement of crank 52, this feature contributingsmooth stopping of the links 44 and fans 40,'which have already brought the blades practically. to a halt.

Figs. 5,6 and-7 illustrate the application of the blade control mechanism of the above construction to a shutter of the type having a single set of blades.- The side elevation of Fig. '7 shows clearly the relationship of the main or mechanism plate I00, the blade cover plate H32 having the necessary clearance grooves, and the mechanism cover plate I04, as well as the power spring I 06 and winding arm or lug I08. As in the prior embodiment, the winding lug is connected by a shaft passing through the main mechanism plate with a latchable crank III) (see Figs. and 6), pivotally connected as at II2 to a short link II I having its opposite end pivotally connected to a transfer lever IIB.

Transfer lever I I6 is itself pivoted as at II8 to the mechanism plate, and it has connected thereto a link I20 which is relatively longer than link IM and which transmits the motion to a fan I22 in all respects similar to the fan do of the previous embodiment. It will be understood that the shutter now being described utilizes a single set of blades I24 each driven through a cranked link I26 connected to one of the fans I22, and that the fans themselves are interconnected by links I28 as in the previous embodiment.

The transfer lever I I6 is provided to permit the use of a connecting link III which is no longer than twice the crank radius of latchable crank IIU, so that at the closing phase of rotation of crank I III, the circle described by the end I I2 of link I I4 about its opposite end will closely approach the circle described by point II2 about the center of rotation of crank II, which produces the gradual deceleration in movement of the parts in the same manner as described above in connection with the previously described embodiment.

In order to latch crank H0 at the end of its operating movement, a spring I38 is secured to plate IIIII and in its unstressed condition has the form shown in Fig. 6. As spring I86 drives crank III] to its iinal position, the end of crank I It (moving in the direction of the arrow in Fig. 6) wipes against a braking spring I32 and ultimately comes up against spring ISII, straightening it out against its fixed backing plate Hi l. The end of spring I32 then drops behind the end of crank IIIl, holding the latter in the position shown in Fig. 5. To release the shutter after spring I86 has been rewound, a lever I36 (Fig. 7) is depressed against the mechanism plate Iiifl, and this lever carries a pin I38 passing through the plate and engageable-With the end of spring I30 to deflect it away from plate m0 and release the crank III which then comes against pin I38 where it is held until pin I38 is retracted by release of spring lever I36. Crank III} then travels through a complete circle until brought to a stop first by wiping along the arcuate portion of spring I32, and then by engaging against spring I3Il, as above described.

- other types and constructions, and that the de- Inspection of spring ISB in Fig. 6 will show that at the initial engagement of crank IIII therewith, the point of bearing of the spring against backing plate I3 5 is relatively remote from the end of the spring, and that as spring I38 is deflected against the backing plate, this point of engagement moves nearer the outer end of the spring, to provide a gradually increasing resistance to further movement of the crank. At the end of the exposure, crank III] has returned to its Fig. 5 position, in which it is held by reason of the fact that the end of spring I32 drops behind the end of the crank and positively prevents any return or rebound movement of the crank.

While the invention has been disclosed herein in connection with certain preferred embodiments thereof, it is to be understood that the principles thereof may be applied to shutters of tails of construction may be widely varied without departing from the spirit of the invention as defined in the appended claims.

I claim:

1. In a camera shutter construction, means defining an exposure aperture, a plurality of shutter blades pivotally disposed in spaced relationship about said aperture to open and close the same, an equal plurality of substantially triangular motion-transmitting members pivotally mounted adjacent respective vertices thereof and outwardly of said respective shutter blades from said aperture, motion-transmitting links pivotally connecting said triangular members at adja cent vertices for operation one by another, an arm pivotally connecting each of said members with its corresponding shutter blade to drive the latter, a driving linkage, and means connecting said linkage to one of said members to impart driving power to said members and said blades.

2. A photographic .shutter comprising a plurality of pivotally mounted blades, a pivotally mounted fan for each of said blades, pivoted on an axis spaced from the corresponding blade axis, means connecting each of said fans with a respective blade, motion transmitting members connecting said fans with one another for simultaneous rotation thereof, a spring driven crank, an intermediate crank, a first link between said spring driven crank and said intermediate crank, and a second link between said intermediate crank and one of said fans, said parts being so arranged that when said blades are in their shutter closing position the point of connection between said second link and said intermediate crank lies to one side of a line joining the point of connection of said second link and said fan with the pivotal axis of said intermediate crank, and the point of connection between said first link and said spring driven crank is in alignment between the point of connection between said first link with said intermediate crank and the axis of rotation of said spring driven crank.

3. A photographic shutter comprising a plurality of pivotally mounted blades mounted about an exposure aperture with their pivotal axes located upon a circle surrounding said aperture, a pivotally mounted sector-shaped fan for each of said blades and having its pivotal mount lying outwardly of said circle with the body portion of each extending outwardly from its pivotal mount, motion-transmitting links pivotally connected between adjacent outer corners of successive ones of said fans, linkage connecting each of said blades with the corresponding fan at a point on the latter intermediate the connections of said motion-transmitting links, and means for driving one of said fans through an arc to open and close all of said shutter blades by reason of force transmitted from fan to fan by said motion-transmitting links.

4. A photographic shutter comprising a plurality of pivotally mounted blades mounted about an exposure aperture with their pivotal axes located upon a circle surrounding said aperture, a pivotally mounted fan for each of said blades having its pivotal mount outwardly of said circle and its body portion extending outwardly from its pivotal mount, motion-transmitting links pivotally connected between adjacent outer corners of successive ones of said fans, linkage connecting each of said blades with the corresponding fan at a point on the latter outwardly-of the pivotal mount of said fan; and means for driving one of said fans-through an arc to open and close all of said shutter blades by reason of force transmitted from'fan-to-fan by said motion-transmitting links.

- 5. A shutter in accordance with claim 4, in which the connections between said motiontransmitting links and each of said fans lie upon an are centered on the pivotal axis of said fan.

6. A shutter in accordance with claim 5, in which the linkage connecting each blade with its fan is pivoted to said fan at a point lying upon the last-named arc.

7. A photographic shutter comprising a plurality of pivotally mounted blades mounted about an exposure aperture with their pivotal axes located upon a" circle surrounding said aperture, a pivotally mounted sector-shaped fan for each of said blades and having its pivotal mount'lying outwardly of said circle with the body portion 'of each extending outwardly from its pivotal'mount, motion-transmitting links pivotally connected between adjacentouter corners of successive ones of said fang-mechanism connecting each of said blades with the corresponding fan and means for driving'one of said fans through an arc'to open 'and close all of said shutter blades by reason of force transmitted from fan to fanby said "motion-transmitting links.

8. A photographic shutter comprising a' plurality of pivotally mounted blades mounted about an exposure aperture with their pivotal axes located upon a circle surrounding said-aperture; a pivotally mounted sector-shaped fan for each of said blades and having its-pivotal mount lying outwardly of said circlewith the body portion of each extendingoutwardly from its pivotal mount, motion-transmitting links piv- =-ota llyconnected between adjacent outer corners of successiveones of said fans, mechanism connecting eachof said blades with the corresponding-fan at apoint on the latter intermediate the connections of said motion-transmitting links, and means'for driving one of said fans through an arc to'open and close all of said shutter blades by reason of force transmitted from fan to fan by said motion-transmitting links.

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